An organic electroluminescence device (hereinafter “electroluminescence” shall be abbreviated as EL) is a spontaneous light emitting device making use of the principle that a fluorescent substance emits light by recombination energy of holes injected from an anode and electrons injected from a cathode by applying an electric field. Since a low voltage-driven organic EL device of a laminate type was reported by C. W. Tang of Eastman Kodak Company (C. W. Tang and S. A. Vanslyke, Applied Physics Letters, Vol. 51, p. 913, 1987), researches on organic EL devices comprising organic materials as structural materials have actively been carried out. Tang et al. use tris(8-hydroxyquinolinol)aluminum for the light emitting layer and a triphenyldiamine derivative for the hole transporting layer. The advantages of a laminate structure include that an efficiency of injecting holes into a light emitting layer can be elevated, that a forming efficiency of excitons formed by blocking electrons injected from a cathode to recombine them can be raised and that excitons formed in the light emitting layer can be shut up. As shown in the above example, a two layer type comprising a hole transporting (injecting) layer and an electron transporting and light emitting layer and a three layer type comprising a hole transporting (injecting) layer, a light emitting layer and an electron transporting (injecting) layer are well known as the device structures of the organic EL device. In such laminate type structural devices, device structures and forming methods are studied in order to enhance a recombination efficiency of holes and electrons injected.
Known as light emitting materials are chelate complexes such as a tris(8-quinolinolate)aluminum complex, coumarine derivatives, tetraphenylbutadiene derivatives, bisstyrylarylene derivatives and oxadiazole derivatives. It is reported that luminescence of a blue color to a red color in a visible region is obtained from them, and it is expected that a color display device is materialized (for example, patent documents 1 to 3).
In recent years, it is investigated in many cases to use energy of a triplet state for EL luminescence by using a phosphorescent compound as a light emitting material. It is reported by the group of Princeton University that an organic luminescence device using an iridium complex as a light emitting material shows a high luminous efficiency (non-patent document 1). Further, an organic luminescence device using a conjugated polymer in addition to the organic luminescence device using the low molecular material described above is reported by the group of Princeton University (non-patent document 2). In this report, luminescence is confirmed in a single layer by making a film from polyphenylenevinylene in a coating system.
As described above, organic EL devices are notably progressing in recent years, and since characteristics thereof are a high luminance at a low applied voltage, a diversification in a luminous wavelength, a high speed response and possibility of preparing a thin and light-weight luminescence device, it is indicated that they can be applied to broad uses.
As organic EL devices are notably progressing, performances required to the light emitting materials are growing high, and fluorene compounds having specific structures are disclosed as a material providing luminescence of a high luminance at low voltage and having an excellent durability in a patent document 4 (Canon Inc.) and a patent document 5 (Mitsui Chemicals Inc.).
However, the light output of a higher luminance and the higher conversion efficiency are required in order to enhance the practical performances. Also, a lot of problems are still involved in terms of durability against a change with the passage of time caused by use over a long period of time and deterioration caused by ambient gas including oxygen and humidity. Further, considering application thereof to full color displays, luminance of blue, green and red colors each having a good color purity are required, but these problems are not still sufficiently solved.    Patent document 1: Japanese Patent Application Laid-Open No. Hei 8-239655    Patent document 2: Japanese Patent Application Laid-Open No. Hei 7-138561    Patent document 3: Japanese Patent Application Laid-Open No. Hei 3-200889    Patent document 4: Japanese Patent Application Laid-Open No. 83481/2004    Patent document 5: Japanese Patent Application Laid-Open No. 43349/2004    Non-patent document 1: Nature, 395, 151 (1998)    Non-patent document 2: Nature, 347, 539 (1990)